Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 120112
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
912 PM EDT FRI JUL 11 2014

.UPDATE...

THE BAND OF LIGHT RAIN WHICH HAS BEEN TRACKING S-SE ALONG THE
MI/IN BORDER THIS EVENING IS OCCURRING IN ADVANCE OF A MID LEVEL
SHORT WAVE IMPULSE AND ALONG THE LEADING EDGE OF A MID LEVEL
THETA-E PLUME. THE FORCING HAS BEEN SLOWLY OUTPACING THE MID LEVEL
MOIST AXIS WHICH HAS CAUSED THE RAIN TO DECREASE IN COVERAGE. THE
FORCING WILL SLIDE ACROSS SOUTHERN LENAWEE AND MONROE COUNTIES
LATE THIS EVENING. CURRENT RADAR TRENDS SUGGEST NOTHING MORE THAN
A BRIEF LIGHT SHOWER...POSSIBLY NOT EVEN AMOUNTING TO 0.01 INCH.
SO A WHOLESCALE FORECAST UPDATE TO RAISE POPS DOES NOT LOOK
JUSTIFIED. THE MID LEVEL MOIST AXIS WILL ADVANCE INTO SE MI
OVERNIGHT. MODEL SOUNDINGS SUGGEST THE MID LEVEL MOISTURE DEPTH
WILL BE SHALLOW WITH A STABLE PROFILE ABOUT THE MOIST LAYER. THERE
WILL ALSO BE QUITE A BIT OF DRY AIR BELOW 700MB /SUPPORED BY THE
00Z DTX SOUNDING/. THUS A DRY FORECAST STILL LOOKS VALID. THE ONLY
UPDATE WILL BE A SLIGHT NUDGE UPWARD IN THE SKY COVER.


&&

.AVIATION...ISSUED 726 PM EDT FRI JUL 11 2014

//DISCUSSION...

ANY REMAINING CUMULUS WILL DISSIPATE OVER THE NEXT FEW HOURS WITH
HIGH CLOUDS STICKING AROUND OVERNIGHT.  SOUTHERLY WINDS WILL ALSO
WEAKEN...BECOMING LIGHT AND VARIABLE TONIGHT.  SCATTERED LIGHT RAIN
SHOWERS CURRENTLY OVER SOUTHERN LAKE MICHIGAN CONTINUE TO DISSIPATE
AS THEY MOVE SOUTHEAST INTO DRIER AIR AND WILL STAY SOUTH OF
DTW/DET/YIP TERMINALS.  VFR CONDITIONS CONTINUE OVERNIGHT INTO
SATURDAY MORNING BEFORE LOWER VFR CLOUDS MOVE IN LATER SATURDAY
AFTERNOON AHEAD OF THE NEXT SYSTEM.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE ON CEILINGS AOB 5000 FT SATURDAY AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 335 PM EDT FRI JUL 11 2014

SHORT TERM...THROUGH TONIGHT

ANOTHER PLEASANT AFTERNOON IS ONGOING THANKS TO NORTHWESTERLY UPPER
FLOW AND THE WESTERN EXTENSION OF A SURFACE HIGH CENTERED OVER
UPSTATE NY. 18Z WATER VAPOR IMAGERY DEPICTS A SHORTWAVE TROUGH
MOVING EWD ACROSS NORTHERN WI...AND ASSOCIATED VIRGA/HIGH-BASED
SHOWERS OVER THE CENTRAL UP. VIRGA/HIGH-BASED SHOWERS ARE ALSO NOTED
OVER SOUTHERN WI. THESE SHOWERS ARE LOCATED IN AN AREA OF LOW-MID
LEVEL WAA AND ARE HAVING TROUBLE REACHING THE GROUND AMID DRY
LOW-LEVEL AIR. WHILE MODEST WAA WILL INCREASE A BIT LATE TONIGHT
OVER SE MI...IT WILL NOT BE AS STRONG AS WHAT IS BEING SEEN WEST OF
HERE. THAT FACT...COUPLED WITH THE LOW LEVEL DRY AIR...WILL LEAD TO
CONDITIONS REMAINING DRY TONIGHT. MID AND HIGH LEVEL CLOUDS WILL BE
ON THE INCREASE...BUT SHOULD NOT BE QUITE AS WIDESPREAD AS WHAT IS
CURRENTLY NOTED TO OUR WEST. WENT PARTLY CLOUDY OVERNIGHT...BUT
COULD HAVE PERIODS OF MOSTLY CLOUDY SKIES. LOWS TONIGHT WILL BE NEAR
TO SLIGHTLY ABOVE NORMAL IN THE LOW TO MID 60S AS DEWPOINTS CREEP UP
TO NEAR 60 BY 12Z. WHAT CLOUD COVER EXISTS...ALONG WITH A LIGHT
SOUTHERLY GRADIENT AS THE SURFACE HIGH CONTINUES MIGRATING
EASTWARD...SHOULD KEEP THOSE LOWS ELEVATED A BIT COMPARED WITH
RECENT NIGHTS.

LONG TERM...

MAJOR FOCAL POINT OF THE WEEKEND FORECAST IS WHEN PRECIPITATION
CHANCES WILL INCREASE ON SATURDAY. THE FORECAST HAS BEEN A LITTLE
EARLY WITH THE MENTION...LIKELY STEMMING FROM SOME FORECAST INERTIA
OF EARLIER SOLUTIONS. OVERALL..THE LATEST FORECAST IS A DRIER ONE
THROUGHOUT 12-00Z SATURDAY. FOR TWO REASONS...MODEL SOLUTIONS HAVE
SLOWED DOWN A HAIR WITH REGARDS TO ADVECTING PRECIPITATION
EASTWARD...AND THE AMOUNT OF DRY IN PLACE IN THE LOWEST 12 TO 15 KFT
AGL. EXPECTING A HIGH AMOUNT SKY FRACTION...HIGH CLOUD VARIETY...BUT
NOT ENOUGH TO BE FRIGHTENED AWAY FROM HIGHER MAX TEMPS...LOW TO MID 80S.

PRECIPITATION CHANCES WILL INCREASE MARKEDLY SATURDAY EVENING...AS A
PRECEDING NOCTURNAL LOW LEVEL JET CYCLE AND PRIOR CLOUD/PRECIPITATION
ADVECTS EASTWARD TOWARD SOUTHEASTERN MICHIGAN. THIS INITIAL ACTIVITY
WILL RESIDE IN THE RIGHT EXIT QUADRANT OF WHAT IS MODELED TO BE AN
OUTSTANDING ANTICYCLONIC ROSSBY WAVE BREAK STRUCTURE.
ALSO...PROXIMITY OF SOUTHEASTERN MICHIGAN TO UPPER LEVEL JET
CORE/NEGATIVE PV ANOMALY WILL BE QUITE SUBSTANTIAL AT LEAST THROUGH
THE FIRST HALF OF THE NIGHT. THIS WILL ALL CHANGE LATE SATURDAY
NIGHT AND DURING THE FIRST HALF OF SUNDAY AS THE UPPER LEVEL JET
STEADILY SPREADS SOUTHWARD ACROSS LOWER MICHIGAN. THE CLOSING
PROXIMITY OF THIS FEATURE WILL THEN PUT SOUTHEASTERN MICHIGAN IN A
GOOD LOCATION TO FEEL THE FULL EFFECTS OF THE FRESH NOCTURNAL LOW
LEVEL JET PUSH/INCREASED CONVERGENCE/MOISTURE TRANSPORT FROM
SATURDAY NIGHT. THIS IS EXPECTED TO RESULT IN A MUCH MORE PRISTINE
ADMISSION OF AN EML BREAKOFF FROM THE CENTRAL PLAINS...INCREASING
INSTABILITY LATE SATURDAY NIGHT AND INVOKING A TOTAL WAVE LIKE
RESPONSE. THIS IS GOOD FOR CATEGORICAL POPS WITH SHOWERS AND
THUNDERSTORMS LATE SATURDAY NIGHT. LATEST SWODY3 HAS EXTREME
SOUTHERN PORTIONS OF THE CWA OUTLOOKED IN SLIGHT RISK...AND THIS
ACCOUNTS FOR THE POSSIBLE THUNDERSTORM ACTIVITY THAT WOULD IMPACT
THOSE AREAS SOMETIME RIGHT AWAY SUNDAY MORNING. GOOD SOAKING
POTENTIAL FROM QPF EXISTS LATE SUNDAY NIGHT...BUT NO REAL EXCESSIVE
RAINFALL RISK TO SPEAK OF.

NEXT WEEK WILL BE MARKED BY BELOW NORMAL TEMPERATURES AND CHANCES
FOR PRECIPITATION THROUGH THE MIDDLE OF THE WEEK WITH CONDITIONS
IMPROVING TOWARDS THE END OF THE WEEK.  UPPER LEVEL LOW AND
ASSOCIATED TROUGH WILL DIG SOUTH OVER THE GREAT LAKES ALLOWING FOR
COOLER AIR TO FILTER IN WITH 850MB TEMPS DROPPING INTO THE SINGLE
DIGITS.  HIGHS ON TUESDAY WILL STRUGGLE TO GET TO 70 DEGREES
ESPECIALLY WITH CLOUDS AND PRECIPITATION OVER THE AREA.  WITH
SOUTHEAST MICHIGAN LOCATED WITHIN THE TROUGH CHANCES FOR SHOWERS
CONTINUE THROUGH THE MIDWEEK BEFORE HEIGHTS BEGIN TO RISE AS UPPER
LEVEL RIDGING BUILDS IN FROM THE WEST TOWARDS THE END OF THE WEEK.
TEMPERATURES LATER IN THE WEEK ARE EXPECTED TO SLOWLY CLIMB BACK
INTO THE MIDDLE AND UPPER 70S.

MARINE...

HIGH PRESSURE WILL PROVIDE LIGHT WINDS AND LOW WAVES TONIGHT. LIGHT
SOUTHERLY WINDS ON SATURDAY WILL BRING WARMER AND MORE HUMID AIR
INTO THE REGION BY LATE IN THE DAY. THE CHANCE FOR SHOWERS AND
THUNDERSTORMS WILL INCREASE OVER THE CENTRAL GREAT LAKES BY LATE
SATURDAY NIGHT AND DURING THE EARLY PART OF SUNDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

UPDATE.......SC
AVIATION.....SS
SHORT TERM...DT
LONG TERM....CB/SS
MARINE.......CB


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).





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